Conventionally, as a seat sliding device for a vehicle that is for adjusting a seat for a vehicle back and forth, a seat sliding device for a vehicle disclosed in Patent Document 1 described below is known. In the lock mechanism of this seat sliding device for a vehicle, the nails of the lock lever tiltably fixed to the upper rail engage the engaging holes of the lower rail and the engaging holes of the upper rail and the like, thereby immovably locking the upper rail relative to the lower rail. When the lock lever is tilted by operation of the operation lever and the nails are pulled out from the engaging holes of the lower rail and the engaging holes of the upper rail and the like, the above-mentioned lock state is released.